The present invention relates to a method and apparatus for wrapping a load with packaging material.
Loads have been stretch wrapped with stretch wrap packaging material by securing a leading end of the packaging material to the load or a turntable clamp, dispensing the packaging material by providing relative rotation between the load and a packaging material dispenser to cause the load to be enveloped by the packaging material, and severing the packaging material between the load and a packaging material dispenser. The relative rotation between the load and the dispenser can be provided either by rotating the load on a turntable, or by rotating the dispenser around a stationary load. Stretch wrapping usually employs a web of stretch film as the packaging material, and the machinery can be either automatic or semi-automatic.
Semi-automatic stretch wrapping machinery requires the operator to attach a leading end of the packaging material to the load for each load to be wrapped. This is typically accomplished by forming a rope in the leading end of the film and then inserting this end between the layers of the load or by tying the end of the packaging material to the edge of the supporting wood pallet or any suitable outcropping on the load. This attachment must be relatively strong since it provides the reaction to force needed to pull the film from the film dispenser during the initiation of the relative rotation between the load and the film dispenser. The attachment or tying of the film makes film removal more difficult after the load has been shipped to its destination.
Automatic stretch wrapping machines are significantly more expensive than semi-automatic machines. The automatic machines typically use film clamps that grip the film web between two opposed surfaces, use electrical or pneumatic actuators to open and close the clamps, typically supply electrical or pneumatic power to the actuators on a turntable through the journal of the turntable, and use hot wires or other expensive cutting devices to cut the film. Such film clamps create a xe2x80x9ctentingxe2x80x9d effect during wrapping due to the distance between the clamp and the load during wrapping, resulting in wasted film and loosely wrapped loads.
In light of the cost of such automatic machines, there is a need for a method and apparatus for wrapping a load with packaging material that operates as effectively as those previously developed to allow automatic release and clamping of portions of the packaging material but which can be manufactured at a lower cost.
Accordingly, the present invention is directed to a method and apparatus for wrapping a load with packaging material which provides advantages over and obviates several problems associated with earlier methods and apparatus for wrapping a load.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention concerns an apparatus for wrapping a load with packaging material, including a dispenser for dispensing packaging material, a rotatable turntable for providing relative rotation between the dispenser and the load to wrap packaging material around the load, and a packaging material holder mounted on the turntable and isolated from any electrical or fluid power source by the rotatable turntable for automatically grasping and releasing portions of the packaging material.
According to another aspect of the present invention, the invention concerns an apparatus for wrapping a load with packaging material, including a dispenser for dispensing packaging material, means for providing relative rotation between the dispenser and the load to wrap packaging material around the load, and a packaging material holder for holding and releasing the packaging material, the packaging material holder being mounted to move upstream with the packaging material in response to force exerted on the packaging material by the packaging material holder to permit the packaging material to sever at a weakened portion between the packaging material holder and the load.
According to a further aspect of the present invention, there is provided a method of wrapping a load with packaging material, including grasping a leading end of packaging material with a packaging material holder mounted on a rotatable turntable and isolated from any electrical or fluid power source by the rotatable turntable, dispensing packaging material from a packaging material dispenser and rotating the turntable to wrap packaging material around the sides of the load, automatically releasing the leading end of the packaging material from the packaging material holder, and automatically grasping a trailing end of the packaging material with the packaging material holder at a point upstream of the leading end.
According to another aspect of the present invention, a method of wrapping a load with packaging material is provided including dispensing packaging material from a packaging material dispenser and providing relative rotation between the dispenser and the load to wrap packaging material around the sides of the load, holding a portion of the packaging material in a packaging material holder, weakening the packaging material between the load and the packaging material dispenser, and severing the packaging material at the weakened portion by tensioning the packaging material between the packaging material dispenser and the load while permitting the packaging material holder to move upstream with the packaging material toward the dispenser.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and other advantages of the invention will be realized and attained by the method and apparatus particularly pointed out in the written description and claims as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and together with the description serve to explain the principles of the invention.